Las Pilitas Nursery

California Native Plants are all we grow!

Blog Contact Us Directions

3232 Las Pilitas Rd
Santa Margarita, CA 93453

Shop For Plants Cart Contents

This website is dedicated to Bert Wilson. His genius continues to inspire us.

Dealing with troublesome Boron soils.


Soils with a level of Boron of 1 ppm or more can be very limiting as most plants hate soil levels of Boron above 2 ppm. Sensitive plants start having problems at 1ppm.  High Boron soils occur in many spots in California, sometimes in spots you'd never guess without a soil analysis. High boron soils can be associated with serpentine soils, such as south of San Luis Obispo, arid areas such as  the west side of the San Joaquin Valley and  Coachella Valley or mountainous areas like  the Mt. Pinos area.
The common treatment for high Boron soils is to leach out the Boron. This is increasingly a problem though as no one wants that boron on there site. So moving the Boron from your site to someone else's is a option in many causes. Also many times the water also has high Boron.  You can try to make it less available by adding gypsum or  playing with the pH. I'm not much of a fan of either. I do not think soil amendments do much over time.
Mulch has helped by pushing the Boron down below root level. But how much mulch can you find and how can you grow row crops with mulch?

Here's a list of Boron Tolerate plants that we have observed along with some that a customer in the Lockwood Valley south of Mt. Pinos. None of these are absolute and every site is different. But they worked at a B of 3-5 ppm.
I always wondered why the hills around San Luis Obispo had little on them. I thought it was serpentine, but it is more likely serpentine and high boron. Only a few native plants can tolerate both. Once it burns it is very hard for the native plants to come back if weeds are present. - grid24_12
The hills around San Luis Obispo have between 2-10 ppm Boron.